Component Of Cropping Systems Research Articles

A Review of Factors Affecting Pod Shattering in Soybean (Glycine max)

Soybean is an important crop in the world cultivated for its oil and protein content. It is a significant component of the small holder cropping system and has the potential to become a major crop produced in Africa. However, its productivity is hampered by a number of biotic and abiotic factors. Among the important biotic factors affecting the yield of soybean is pod shattering. Pod shattering is the opening of mature pods along the dorsal or ventral sutures (located along the length of the pod) when the crop matures or during harvesting resulting in seed dispersal. It is a quantitative trait that is influenced by one major gene and a few minor genes and is also highly heritable. It can cause yield losses of up to100%. Apart from causing yield losses, pod shattering may pose a challenge to the crop rotations in the following seasons as seeds from shattered pods tend to emerge as volunteer weeds. There are a number of factors that are linked to pod shattering. An overview of the morphological, anatomical, environmental and genetic aspects associated with pod shattering in soybean is discussed in this review. Understanding all the factors underlying pod shattering in depth is key in breeding soybean varieties that delay to shatter. This can help breeders in knowing which approach to take in breeding for soybeans with pods that delay to shatter. Breeding strategies can focus on manipulating morphological, biochemical and anatomical traits.

Management of tree fodder banks for quality forage production and carbon sequestration in humid tropical cropping systems – An overview

Livestock forms an integral component of humid tropical cropping systems, providing food and financial security, employment, and insurance against crop failure for small scale farmers. However, livestock sector is seriously constrained by the drastic decline in fodder base and high cost of feeds, incurring huge economic loss to farmers. Hence fodder production should be intensified in cropping system by including alternate feeds like nutrient rich fodder trees and shrubs to supplement conventional fodder. Fodder trees serve as a potential source of quality green fodder to livestock especially during lean periods. Moreover, tree leaves can be cheaper feed supplements than the commercial concentrates and can easily be grown by the small-holder farmers. Leucaena, mulberry, kadamba, calliandra, agathi, moringa and gliricidia are promising fodder tress by virtue of their nutritive foliage, fast growing nature with higher biomass production, amenable to heavy pruning, good coppicing ability and easy management. Moreover, these trees can be grown in close hedgerows as fodder banks in integration with existing crops to maximize productivity in land crunch humid tropical areas. Enhancing tree cover in cropping systems also offers ecosystem services like enhanced carbon storage and associated global warming issues. Forage and nutrient yields, and carbon accretion can be substantially elevated and crop–tree competition can be minimized by appropriate stand management practices and proper regulation of overstorey and understorey components. Extensive studies conducted on tree fodder bank establishment, management and their productive and protective functions in humid tropical cropping systems of South India are reviewed in this paper.

Effect of in situ soil moisture conservation practices on maize and its crop residue incorporation on yield and economics of succeeding transplanted rice Var. ADT 46

Crop residue incorporation is a key component of sustainable cropping systems. It reduces the adverse effects of residue burning and enhances soil fertility. Effective usage of crop residue in the field and proper management are required. With this background, a field experiment was conducted during 2020 – 21 in the maize-rice cropping sequence at Annamalai University Experimental Farm, Department of Agronomy, Faculty of Agriculture, Annamalai University, Annamalai Nagar, Tamil Nadu to find out the residual effect of different mulching practices adopted in preceding maize crop and maize stubble incorporation on the growth, yield and economics of transplanted rice Var. ADT 46. The field experiment was conducted in Factorial Randomized Block Design with three replications. In factor I, soil moisture conservation in preceding maize crop viz., mulching of sugarcane trash, water hyacinth, hydrogel and control were allotted. In factor II, different levels of maize crop stubble incorporation on rice viz., 0, 33, 66 and 100% were provided. Water hyacinth mulched plot (M3) to the preceding crop registered significantly (þ <0.05) higher yield parameters, yield and economic returns of succeeding rice. The lower values were observed in unmulched (M1) plot. With respect to maize crop stubble incorporation on rice crop, the incorporation of 66% (SI3) of maize stubble registered higher yield parameters, yield and economic returns. In the interaction effects, mulching with water hyacinth to preceding maize + maize crop stubble incorporation at 66% in rice crop (M3SI3) recorded significantly (þ <0.05) higher yield parameters, yield and economic returns than other treatments. The lowest values were recorded with an unmulched + 100% crop residue incorporated (M1SI4) plot. Mulching the preceding maize crop with water hyacinth at a rate of 12 t ha-1 and incorporating 66% maize stubble into the transplanted rice (M3SI3) had a remarkable yield advantage and financial rewards.

Enrichment in biodiversity and maturation of the soil food web under conservation agriculture is associated with suppression of rice-parasitic nematodes

Meloidogyne spp. and Hirschmanniella spp. are among the most damaging plant-parasitic nematodes (PPNs). They threaten rice production, the main staple food in Asia. Cropping systems that promote natural biocontrol and plant tolerance to diseases are put forward as sustainable solutions to protect rice from these pests. In particular, cropping systems managed under conservation agriculture (CA) are promising because they improve soil health and functioning. We investigated the effects of two cropping system components in a Cambodian field, (i) CA practices, i.e., no-tillage with a cover crop Stylosanthes guianensis (cv. Nina), versus conventional plow-based tillage with no cover crop, and (ii) using IR504, IR64, Azucena and Zhonghua 11 rice varieties, on PPNs in roots and on communities (bacteria, fungi and nematodes) in the rhizosphere. We used a sequencing approach via amplicon barcoding to target microbial marker genes (16 S and ITS rRNA gene) and a microscopic approach to identify and quantify nematodes in the rhizosphere compartment. The variety had less effect than agricultural practices on the infection by PPNs and on the assembly of the three rhizosphere communities. Under CA, the abundance of PPNs extracted from the roots was reduced by 88%. Soil quality was substantially improved (+83% of total Kjeldahl nitrogen, +34% of available phosphorus, +10% of exchangeable potassium, +110% of soil organic carbon, +30% for the cation exchange capacity), thus providing more basal resources for microbial decomposers, especially fungi (+164% putative saprotrophs). Characterization of the three rhizosphere communities revealed a shift in the structure associated with soil enrichment. Both microbial richness (+3% for bacteria and +38% for fungi) and diversity (Shannon index, +11% for fungi and +5% for nematodes) increased. The relative abundance of taxa was modified by CA with notably more mycorrhizal fungi (+329% Glomeromycota spp.) and fewer Pratylenchidae nematodes (−92% Hirschmanniella spp.) in the rhizosphere. The reassembly of the communities using CA was associated with regulation of PPN populations. The reduction in Meloidogyne spp. abundance in roots (−64%) was correlated with the maturity of the food web (maturity index, +10% under CA) and with the increase in the relative abundance of omnivorous nematodes in the rhizosphere (+68% under CA). Seven years of CA in this field enabled the whole soil food web to mature thus creating a favorable niche for potentially predatory nematodes and microbes antagonistic against PPNs. This study confirms that CA is an alternative to nematicides to limit infection by PPNs in rice cropping systems.

High-Density DArT Markers and Phenotypic Characterization of Cowpea Accessions (Vigna unguiculata (L.) Walp)

Cowpea (Vigna unguiculata (L.) Walp) is an important component of most traditional cropping systems in the tropics. It provides leafy vegetables and/or grains and forages and acts as a cover crop. We characterized 16 cowpea accession collections in Ghana using agromorphological traits and high-density silicoDArT markers for breeding and efficient conservational purposes. Principal component analysis indicated pod, leaf, and seed characters such as pod length, seeds per pod, terminal leaves shape, number of leaves, hundred seed weight, and seed weight per plant as discriminatory traits in revealing the variation among the accessions. Trait association analysis revealed a significant correlation between the pod number, pod length, seeds per pod, number of leaves, and seed weight per plant that could allow the selection to improve the grain yield. Moderate to high broad-sense heritability and genetic advance observed for most of the traits indicate that the selection would result in foreseeable genetic improvement. The 9,706 silicoDArT markers used in the study were able to reveal genetic variation among the tested cowpea collections. Accessions GH5039 and GH6056 were established as duplicates based on the silicoDArT markers, which could enhance efficient germplasm utilization and conservation. Accessions GH3685, GH3674, and GH4541 were identified for high leaf and pod production and high seed yield per plant, which could be good candidates for dual purpose cowpea production, which is common in the subsistence farming system.

Effects of conservation agriculture maize-based cropping systems on soil health and crop performance in New Caledonia

Conservation agriculture (CA) is one strategy with which both sustainability and productivity can be achieved by improving soil health. However, linkages between practices, soil health and cropping system performance remain poorly disentangled. We assessed the relationships between soil health and cropping system performance for three maize-based cropping systems in New Caledonia. Two CA systems, one with direct seeding into a mixed species dead mulch (CA-DM) and one into a stylo living mulch (CA-LM), were compared to a conventional tillage (CT) system. CA vs. CT experiment started in 2011, whereas the differentiation between CA-DM and CA-LM was initiated in 2017 only. In 2018, soil health was evaluated using Biofunctool®, a set of ten in-field tools that assess soil carbon transformation, structure maintenance and nutrient cycling functions. The performance of the three cropping systems were assessed by monitoring weeds, maize growth and yield components. Structural equation modelling (SEM) was used to disentangle the links between agricultural management, soil health and cropping system performance. Soil structure maintenance and nutrient cycling functions were higher under CA-DM and CA-LM than under CT, and carbon transformation function was higher under CA-DM than under CT and CA-LM. Overall, the soil health index (SHI) was 1.3-fold higher under CA systems than under CT. Cropping system management had both direct and indirect effects on soil functioning and crop productivity leading to a 1.3-fold higher yield under CA than under CT. The direct and indirect effects of CA systems on soil health had positive impacts on ecosystem services (i.e., productivity, weed regulation and soil ecosystem services). Such integrative approaches that account for the relationships and possible trade-offs between cropping system components enable a better understanding of the effects and the performance of practices, and support adaptive agricultural management.

Temperature-based prediction of harvest date in winter and spring cereals as a basis for assessing viability for growing cover crops

• The growth and viability of cover crops depends on autumn growth duration. • The viability of growing cover crops was assessed with a phenology model. • The phenology model predicts harvest time of spring and winter cereals. • The harvest time varies more spatially across Denmark than between years. • Simulations show that cover crops can be reliably established in southern Denmark. Cover crops are an important component of sustainable cereal cropping systems by providing nutrient retention and improving soil quality. However, the successful establishment and growth of cover crops depend on a timely harvest of the preceding annual crops. To assess the viability of growing cover crops in Denmark, a phenology model was developed, calibrated, cross-validated and applied to predict the harvest date of spring barley and winter wheat in Denmark using data from field experiments in Denmark during 1991 to 2018. A simple phenology model was used for the period from sowing to maturity, and this was extended to simulate the duration from maturity to harvest. This extended model was used to predict the harvest date in the ongoing season, and it provides the capability for assessing the performance of cover crops as a basis for improved cover crop management. The model uses temperature sums and day length to calculate the developmental rate of spring barley from sowing to harvest and for winter wheat from 1st January to harvest. The standard deviation of the estimated harvest date based on the uncertainty of the model parameters was 10-14 days and 1-4 days for spring barley and winter wheat, respectively. The model was evaluated using historically recorded temperature data (20 years, 1999–2018) to simulate harvest date, which was within the range of observed harvest dates. The interannual range of estimated harvest dates is 7–10 days for spring barley and 5–10 days for winter wheat. This interannual variation of harvest date was lower than the spatial variation across the country. The model can be used for forecasting cereal harvest time and thus readiness for autumn field operations, including the establishment of cover crops. Simulations of growing degree days from date of harvest to 1 November shows that cover crops can be reliably established in southern parts of Denmark to ensure low nitrate leaching. Advancing the harvest date to the date of physiological maturity of the cereals would allow the establishment of efficient cover crops in all years in the entire country.

A Study on Sustainable Modules for Year-Round Green Fodder Production under Irrigated Conditions

Zonal Agricultural Research Station, Vishweswaraiah Canal Farm, Mandya, conducted "Studies on sustainable modules for year-round green fodder production under irrigated conditions" throughout the kharif, rabi, and summer seasons of 2018–19 and 2019–20. The experiment had three replicates and was set up in a randomized whole block design with fifteen fodder cropping system components. Green fodder yield (1636 q ha-1 year-1), dry fodder yield (321 q ha-1 year-1), carbon sequestration (24.87 Mg ha-1) and net returns (Rs. 2,14,232 ha-1 year-1) were all significantly higher for the BN hybrid + Lucerne (2:8) perennial system than they were for the BN hybrid + Cowpea (2:8) perennial system (1552 q ha-1 year-1, 308 q ha-1 year-1, 24.35.

Cover crops reduce drainage but not always soil water content due to interactions between rainfall distribution and management

Cover crops are a potential component of agroecological cropping systems, since they may render crop rotations more sustainable. They simultaneously provide multiple ecosystem services, such as decreasing nitrate leaching, decreasing erosion, and increasing soil organic matter. However, cover crops increase evapotranspiration and reduce drainage, which results in a potential disservice for groundwater recharge. Little attention has focused on management of cover crop residues after destruction or their influence on water flux dynamics, particularly in dry and temperate climates. The objective of our study was to analyze and quantify the impact of cover crop management on soil water content and water flux dynamics to understand the main mechanisms of system functioning. We combined a two-year field experiment with crop-model simulations. We performed the field experiment in southwestern France that compared three cover crop treatments, with bare soil as the control. The treatments included (1) living cover crops lasting ca. 9 months from August-April, (2) crushing cover crops in November and leaving them as mulch on the soil, and (3) plowing up cover crops in November to promote residue decomposition and the green manure effect. The STICS soil-crop model was used to predict water fluxes that were not measured and to perform a 20-year independent simulation study based on recent climate series for the experimental site. Our main results indicated that cover crops (1) always reduce water drainage by 20-60 mm compared to that under bare soil; and (2) could significantly reduce soil water content (0-120 cm deep) for the next cash crop by a mean of 20-50 mm, and up to 80 mm in dry spring conditions, but early destruction could decrease this negative impact. The simulations clearly showed that the interaction between climate variability, i.e., rainfall distribution during the fallow period, and cover crop management should be considered to explain the impact of inter-annual variability on the water balance. Thus, destroying cover crops mechanically in late autumn and retaining the residues as mulch could be a good compromise between the multiple services the cover crop provides during the fallow period and avoiding the negative impact on soil water availability for the next cash crop.

Agronomic responses of ratoon rice to nitrogen management in central China

Rice ratooning is becoming an important component of rice cropping system in central China because of its low production costs. However, low and unstable grain yield in ratoon season has limited the wide adoption of this technology. Nitrogen (N) management is the most critical in improving the grain yield of rice crops. The objective of this study was to compare the effects of different N treatment on the grain yield and yield attributes of ratoon crop (RC). Two widely planted varieties, Liangyou6326 (LY6326) and Huanghuazhan (HHZ), were grown for rice ratooning in field experiments in Qichun County, Hubei Province, central China in 2016 and 2017. The grain yield of RC ranged from 2.96 to 6.49 t ha−1 across N treatments, varieties, and years with total growth duration of 61 to 84 d in the ratoon season. Application of 100 kg N ha−1 at 15 d after heading of the main crop (MC) for promoting bud development (Nbud) increased the grain yield of RC by 12.7–55.4%. The yield improvement by Nbud was attributed to increased panicles m−2 in the ratoon season. Application of 100 kg N ha−1 at 1–2 d after cutting of MC for promoting the development of regenerated tillers (Ntiller) increased the grain yield of RC by 11.5–35.5% only when Nbud was not applied, and the yield improvement was due to increased panicles m−2 or spikelets panicle−1 or both in the ratoon season. The N rates in MC (100 vs. 200 kg N ha−1) had relatively small and inconsistent effects on the grain yield of RC. Our results indicated that both Nbud and Ntiller were critical for improving the grain yield of RC, although Nbud was more effective than Ntiller under the conditions of our study.

Land Suitability Assessment using GIS for Davana (Artemisia pallens) Cultivation in Karnataka, India

Davana is one of the commercially important aromatic crops grown in Karnataka state, India. Agro-ecological conditions of davana growing areas of Karnataka state was characterized and evaluated. Soil parameters were correlated with herbage yield, oil content and its quality to establish soil-site suitability criteria. To identify the suitable zones for davana cultivation elsewhere in Karnataka, a GIS based agro-ecological evaluation was carried out by using soil resource information (121 soil mapping units on 1:250 K scale) of Karnataka state. Each mapping unit was evaluated by matching soil-site suitability criteria with climate and soil parameters to identify the suitable areas for davana cultivation. Around 45.2 lakh ha area is highly suitable, 65.3 lakh ha is moderately suitable, and 54.2 lakh ha is marginally suitable for davana cultivation. Highly and moderately suitable areas need to be focused for expansion of davana as a component of major cropping or farming systems and also to establish forward and backward linkages.

Assessing climate adaptation options for cereal-based systems in the eastern Indo-Gangetic Plains, South Asia

AbstractNew farming systems and management options are needed in South Asia as the intensive rice–wheat production system is set to become increasingly unsustainable under climate change. In the current study, six cropping systems options/treatments varying in tillage, crop establishment method, residue management, crop sequence and fertilizer and water management were evaluated using a cropping systems model under current (1980–2009) and future (2030 and 2050) climate scenarios in the state of Bihar, India. The treatments were current farmers' practice (CP), best fertilizer and water management practices, zero tillage (ZT) with no crop residue retention, ZT with partial crop residue retention (ZTPR), future conservation agriculture-based rice–wheat intensive cropping system (FCS-1) and future conservation agriculture-based maize–wheat intensive cropping system (FCS-2). The results indicate that climate change is likely to reduce rice–wheat system productivity under CP by 4% across Bihar. All the crop management options studied increased yield, water productivity and net returns over that of the CP under the current and future climate scenarios. However, the ZTPR treatment gave significantly higher relative yield, lower annual yield variability and a higher benefit-cost-ratio than the other treatments across cropping system components and climate periods. Although all the new cropping system treatments had a positive yield implication under the current climate (compared to CP), they did not contribute to adaptation under the future climate except FCS-2 in wheat. It is concluded that adaptation to future climate must integrate both cropping system innovations, and genetic improvements in stress tolerance.

Maize Residue Removal and Cover Crop Effects on Subsequent Soybean Crops

Core Ideas Corn residue removal and cover crop effects on soybeans were measured. Treatments had no effects in years with average temperature and precipitation. Residue removal reduced soybean yield in years characterized by drought. Cover crops also reduced soybean yield in years characterized by drought. Residue management and cover crops are important cropping system components. Maize (Zea mays L.) residue removal and cover crop effects on soybean [Glycine max (L.) Merr.] seed moisture at harvest, grain yield, and seed mineral concentrations were examined. Maize residue removal treatments [low‐residue removal (LRR) (grain harvest only), medium‐residue removal (MRR) (stalks chopped and baled after grain harvest), and high‐residue removal (HRR) (stalks cut and removed as silage)] under no‐till maize/soybean rotations were established near Brookings, SD, in 2000. Subplot treatments, begun in 2005, were the absence or presence of the cover crops fall‐planted slender wheatgrass [Elymus trachycaulus (Link) Gould ex Shinners] in maize and hairy vetch [Vicia villosa (Roth)] plus oats (Avena sativa L.) in soybean. Soybean data from 2009 through 2012 were evaluated. Across years and cover crops, LRR maintained 3587 ± 280 kg ha−1 preseason maize residue, MRR had 2269 ± 227 kg ha−1, and HRR had 1414 ± 172 kg ha−1. Grain moisture was greater (P = 0.03) in LRR (119.6 ± 1.8 g kg−1) than MRR (114.0 ± 1.4 g kg−1) or HRR (114.7 ± 1.5 g kg−1). Grain N was less (P = 0.04) under LRR (62.4 ± 0.5 g kg−1) than MRR (63.4 ± 0.6 g kg−1) or HRR (63.8 ± 0.5 g kg−1). Only during 2012, which had a warm and very dry summer, did MRR (3294 ± 88 kg ha−1) or HRR (3363 ± 141 kg ha−1) have less grain yield than LRR (3766 ± 145 kg ha−1). Cover crops reduced yield in 2012 (3233 ± 78 kg ha−1 with cover crops; 3716 ± 102 kg ha−1 without). Maize residue removal or cover crop cultivation reduced yield only during a growing season with a warm and very dry summer.

Differentiation of Life-History Traits among Palmer Amaranth Populations (Amaranthus palmeri) and Its Relation to Cropping Systems and Glyphosate Sensitivity

Palmer amaranth’s ability to evolve resistance to different herbicides has been studied extensively, but there is little information about how this weed species might be evolving other life-history traits that could potentially make it more aggressive and difficult to control. We characterized growth and morphological variation among 10 Palmer amaranth populations collected in Florida and Georgia from fields with different cropping histories, ranging from continuous short-statured crops (vegetables and peanut) to tall crops (corn and cotton) and from intensive herbicide use history to organic production. Palmer amaranth populations differed in multiple traits such as fresh and dry weight, days to flowering, plant height, and leaf and canopy shape. Differences between populations for these traits ranged from 36% up to 87%. Although glyphosate-resistant (GR) populations collected from cropping systems including GR crops exhibited higher values of the aforementioned variables than glyphosate-susceptible (GS) populations, variation in traits was not explained by glyphosate resistance or distance between populations. Cropping system components such as crop rotation and crop canopy structure better explained the differences among populations. The higher growth of GR populations compared with GS populations was likely the result of multiple selection forces present in the cropping systems in which they grow rather than a pleiotropic effect of the glyphosate resistance trait. Results suggest that Palmer amaranth can evolve life-history traits increasing its growth and reproduction potential in cropping systems, which explains its rapid spread throughout the United States. Furthermore, our findings highlight the need to consider the evolutionary consequences of crop rotation structure and the use of more competitive crops, which might promote the selection of more aggressive biotypes in weed species with high genetic variability.

Increased yield stability of field-grown winter barley (Hordeum vulgare L.) varietal mixtures through ecological processes

Crop variety mixtures have the potential to increase yield stability in highly variable and unpredictable environments, yet knowledge of the specific mechanisms underlying enhanced yield stability has been limited. Ecological processes in genetically diverse crops were investigated by conducting field trials with winter barley varieties (Hordeum vulgare), grown as monocultures or as three-way mixtures in fungicide treated and untreated plots at three sites. Mixtures achieved yields comparable to the best performing monocultures whilst enhancing yield stability despite being subject to multiple predicted and unpredicted abiotic and biotic stresses including brown rust (Puccinia hordei) and lodging. There was compensation through competitive release because the most competitive variety overyielded in mixtures thereby compensating for less competitive varieties. Facilitation was also identified as an important ecological process within mixtures by reducing lodging. This study indicates that crop varietal mixtures have the capacity to stabilise productivity even when environmental conditions and stresses are not predicted in advance. Varietal mixtures provide a means of increasing crop genetic diversity without the need for extensive breeding efforts. They may confer enhanced resilience to environmental stresses and thus be a desirable component of future cropping systems for sustainable arable farming.

Genetic diversity and trait genomic prediction in a pea diversity panel.

BackgroundPea (Pisum sativum L.), a major pulse crop grown for its protein-rich seeds, is an important component of agroecological cropping systems in diverse regions of the world. New breeding challenges imposed by global climate change and new regulations urge pea breeders to undertake more efficient methods of selection and better take advantage of the large genetic diversity present in the Pisum sativum genepool. Diversity studies conducted so far in pea used Simple Sequence Repeat (SSR) and Retrotransposon Based Insertion Polymorphism (RBIP) markers. Recently, SNP marker panels have been developed that will be useful for genetic diversity assessment and marker-assisted selection.ResultsA collection of diverse pea accessions, including landraces and cultivars of garden, field or fodder peas as well as wild peas was characterised at the molecular level using newly developed SNP markers, as well as SSR markers and RBIP markers. The three types of markers were used to describe the structure of the collection and revealed different pictures of the genetic diversity among the collection. SSR showed the fastest rate of evolution and RBIP the slowest rate of evolution, pointing to their contrasted mode of evolution. SNP markers were then used to predict phenotypes -the date of flowering (BegFlo), the number of seeds per plant (Nseed) and thousand seed weight (TSW)- that were recorded for the collection. Different statistical methods were tested including the LASSO (Least Absolute Shrinkage ans Selection Operator), PLS (Partial Least Squares), SPLS (Sparse Partial Least Squares), Bayes A, Bayes B and GBLUP (Genomic Best Linear Unbiased Prediction) methods and the structure of the collection was taken into account in the prediction. Despite a limited number of 331 markers used for prediction, TSW was reliably predicted.ConclusionThe development of marker assisted selection has not reached its full potential in pea until now. This paper shows that the high-throughput SNP arrays that are being developed will most probably allow for a more efficient selection in this species.Electronic supplementary materialThe online version of this article (doi:10.1186/s12864-015-1266-1) contains supplementary material, which is available to authorized users.

Maize residues, soil quality, and wheat growth in China. A review

Crop residue retention is a key component of sustainable cropping systems. In recent years, retention of crop residue is a means of improving soil quality and nutrient capacity and reducing the adverse effects of residue burning. Maize–wheat rotation is a major double-cropping system practiced on more than one fifth of agricultural lands worldwide. Currently, more than 50 % of maize residues are retained immediately after harvesting. In China, this practice has beneficial effects on soil properties and productivity of the succeeding wheat crop. However, increasing the retention of maize residues without proper soil management has also led to a series of concerns, such as short-term nitrogen immobilization, rapid moisture loss, and high susceptibility to freezing during winter as a result of increased soil porosity. Therefore, other practices for maize residue retention are needed to promote wheat growth and the release of nutrients. This article reviews recent developments in China concerning the consequences of maize residue retention on the physical, chemical, and biological properties of soil quality and the growth, productivity, and quality of wheat. Major patterns of maize residue retention are discussed. In particular, this review provides three complementary approaches for maize residue management.

Using a sensitivity analysis of a weed dynamics model to develop sustainable cropping systems. II. Long-term effect of past crops and management techniques on weed infestation

SUMMARYBoth scientists and farmers are confronted by a similar question: which current and past cropping system components will influence the present weed flora, and how? This information is necessary to optimize both cropping systems for weed control, and quality and cost in surveys and monitoring schemes. The present study addressed these questions with a sensitivity analysis to input variables of a cropping system model,AlomySys, that predicts weed dynamics in interaction with pedo-climatic conditions. The study ranked cropping system components according to their impact on weed infestation in winter wheat, showing for instance that though crop succession was crucial, current and past tillage strategies influenced grass weed densities even more. Crops were not only ranked as a function of the resulting weed risk but the latter was also linked to crop species traits, i.e. crop type, usual sowing period and emergence speed. A previous winterv.spring crop thus increased weed density by 72% in the following winter wheat; a late-sownv.early sown winter crop by 26%, a slowv.fast-emerging winter crop by 17%, and a lower competitive ability by 9%. Similarly, the characteristics of each crop management technique (tillage, catch crop, secondary crop, mowing, mechanical weeding, herbicides, nitrogen fertilizer, manure and harvest) were quantified. For instance, the timing of the first tillage operation was crucial prior to the analysed winter wheat crop while the choice of the tool used even 5 years previously still influenced weed infestation in the current year; a catch crop prior to previous spring sown crops reduced the current infestation regardless of catch crop sowing dates and densities, but the reductive effect could be lost if the field was tilled several times to destroy the catch crop. The advice synthesized here and in a companion paper (Colbach & Mézière 2012). will be valuable to design innovative, integrated cropping systems, indicating (1) which cropping system components to modify to produce the largest effect, (2) for how long past practices must be considered when choosing current options and (3) the optimal options for the different management techniques. Points (1) and (2) are also valuable to identify data to record in surveys, though still resulting in a total of 232 variables. In a second step, these detailed variables were therefore simplified and aggregated to determine a smaller set of 22 synthetic variables easily recorded in surveys, such as the proportion of winter and spring crops during the last 10 years (instead of the actual crop sequence), the proportion of crops sown in summer, early autumn, late autumn, early spring and late spring during the last 5 years (instead of exact sowing dates), the ploughing frequency (instead of ploughing dates and characteristics), the mean number of herbicide sprayings per year (instead of dates), etc. This reduced survey list will reduce the cost of surveys as well as increase the number and quality of surveys as more farmers will be ready to participate and there will be fewer uncertainties in the answers.

Improving Soil Quality

Abstract Future advancements in crop production will rely on increased understanding of ecological principles that control interactions among cropping system components. Our interest in linking soil quality and weed management derives from the belief that greater understanding of key processes and properties that define soil-weed relationships will lead to the design of agroecosystems with greater capacity and opportunity to suppress weeds. We identified seed-bank persistence, seedling establishment, and interspecific interference as key processes that affect annual weed population dynamics. We then examined how soil processes and properties can affect each of these factors and how, in turn, soil-improving management practices and cropping system design may affect weed dynamics. We established weed-related soil management objectives as: (i) reducing the persistence of seeds in the soil; (ii) reducing the abundance of safe-sites for weed establishment and the filling of available sites; and (iii) reducing ...

Yield response and stability among cowpea genotypes at three planting dates and test environments

Cowpea (Vigna unguiculata (L.) Walp.) is one of the important food legumes and a valuable component of the traditional cropping systems in the semiarid tropics. Its productivity is generally low since farmers still grow unimproved landraces as a result of unavailability of improved and locally adapted cultivars. The objective of this study was to determine the relative yield response and stability among selected improved cowpea genotypes to make recommendation for wide or specific adaptation. Field experiments were conducted at three locations, three planting dates using ten diverse cowpea genotypes in South Africa during 2005/2006. The experiments were laid out in the randomized complete block design with three replications. Results showed significant interactions (P≤0.01) among genotypes, planting dates and locations for seed yield. The average yield varied from 2583.37 to 3997.78 kg/ha. Genotypes Pan311, CH14 and IT18E-16 were identified with high seed yield measured at 3997.78, 3777.15, and 3751.48 kg/ha, respectively. These genotypes were the most stable yielding that would be suitable for production under these or other similar environments in South Africa. Key words: Cultivar superiority, cowpea, seed yield, South Africa, stability, Vigna unguiculata.